Covalent grafting synthesis of molecularly imprinted covalent organic framework for selective removal of clenbuterol from aqueous medium and milk sample

Clenbuterol (CLB) is a bronchodilator for treating respiratory disorders. However, the irrational use of CLB in animal feeding can cause serious risks to human health. The development of selective and efficient adsorbent for CLB removal is of great significance. Herein, we report a convenient covalent grafting approach for the fabrication of molecularly imprinted covalent organic framework (COF) for selective adsorption and removal of CLB from environmental water and milk samples. By integrating the merits of both molecularly imprinted polymers (MIPs) and COFs, the molecularly imprinted COFs named BatBt-MIPs (2,5-bis(allyloxy)terephthalohydrazide, Bat; 1,3,5-benzenetricarboxaldehyde, Bt) presented the alluring traits of large surface area, tailored-made binding sites, uniform pore structure, and good selectivity for CLB. The adsorption equilibrium for CLB on BatBt-MIPs was quickly reached within 20 min and followed pseudo-second-order kinetic model. BatBt-MIPs showed a CLB adsorption capacity of 15.45 mg/g, which is about 3.7 times higher than that of non-imprinted COFs (BatBt-NIPs). Compared with BatBt-NIPs, BatBt-MIPs present improved adsorption selectivity for template CLB. Selective removal of CLB from complex environmental water and milk samples on BatBt-MIPs was also realized. This work provided a new covalent grafting approach to construct novel molecularly imprinted COFs and highlighted the great potential of COF-MIPs in contaminants elimination.